The present invention relates to the field of biodegradable hydrophilic nonwoven absorbents and more particularly to microfiber biodegradable absorbents prepared by the electrohydrodynamic method from blends of synthetic biodegradable polyesters and poly (N-vinyl) lactams which can be used for a variety of applications including wounds and burns dressings, drug carriers and for cosmetic applications.
It has been known to use poly (N-vinyl) pyrrolidone (PVP) complexes with polyurethanes to yield hydrophilic materials, which can be used as wound dressings or in cosmetic preparations. For example, U.S. Pat. No. 5,156,601 discloses a dressing, which includes a tacky gel of polyurethane and a poly (N-vinyl) lactam such as PVP. U.S. Pat. No. 5,420,197 describes hydrophilic gels formed by poly (N-vinyl) lactams, such as PVP, and chitosan. U.S. Pat. No. 6,121,375 disclose hydrophilic gel-like materials of PVP and polyaldehyde. Other references of general background interest include U.S. Pat. No. 5,206,322. All these materials are gel-like and non-biodegradable.
Although some of these hydrophilic materials can be used for wound dressings and other surgical and cosmetic applications, many hydrophilic materials known in the arts are hydrophilic gels that are non-biodegradable, and most of them are reversible.
It has also been known to make nonwoven fibrous-porous material on the base of a blend of poly (N-vinyl) pyrrolidone (PVP) and cellulose diacetate in component weight ratio of 1:(4-10) with high porosity and high moisture absorption prepared “in electrostatic field by continuous supply of an electrically charged polymeric solution through a nozzle” (Pat. RU No. 2111300). But this material is nonbiodegradable.
There is also known, Pat. RU No. 2031661, a microfibrous wound-healing remedy used for first and outdoors aid, prepared by the electrohydrodynamic method. The remedy comprises a composition of poly-d.l-lactide, poly (N-vinyl) pyrrolidone and a powdered sorptive material like polysaccharides networks, polyacrylates, cellulose esters or polyvinyl alcohol derivatives. The material could absorb 5-8 g/g water or blood; exhibited haemostatic abilities within 40 seconds and moderate wound healing effects. But introduction of nondegradable or slow degradable components such as polyvinyl alcohol derivatives into this material significantly decreased its biodegradation ability and limited its use for external application.
There is also known, Pat. RU No. 2120306, a totally biodegradable two layer dressing for wounds and burns consisting of a baking thin film layer (25-30 mkm) prepared from copoly (lactide-caprolactone) or copoly (lactide-glycolide) with a lactide/caprolactone or lactide/glycolide ratio of at most 50% w and a wound facing microfiber absorbent layer comprising a polylactide and poly (N-vinyl) pyrrolidone blend with a ratio of polylactide/poly (N-vinyl) pyrrolidone from 90/10 to 70/30 w/w. The microfiber absorbent layer is deposited on the film by the electrohydrodynamic method. The facing microfiber layer may also contain antiseptic, analgesic drugs and proteolysis ferments. The dressings described can absorb water and any biological liquids, including blood, at most 12 g/g and biodegrade within 12-36 days. However the vapor penetration of such dressings is at most 3.1 mg/cm2 hour which precludes their use as dressings for wounds and burns that exhibit intensive “breathing”, for example, large external fresh burns, bleeding wounds or different kinds of external injuries. Furthermore these dressings have poorly controllable time of degradation, which limits their application in the treatment of wounds and/or burns, and especially in the treatment of internal wounds. Better control over the degradation time is desirable.
There is also known a microfiber biodegradable polylactide web prepared by the electrospinning method from a polymer solution. The polymer concentration is 4-6% w. The voltage is 33-60 kV; the average fiber diameter is about 1 μm (See the article in Proceeding of the ACS, PMSE, p. 115, Mar. 26-30, 2000). But there is no evidence of any hydrophilic or bioactive properties of such a web. According to the article a solution of polylactide in dichloromethane was placed in a syringe. The syringe was positioned with its needle pointing down, The piston of the syringe was moved down with a controlled velocity by a motor. The negative pole was set at the metal capillary of the syringe and the positive pole on the substrate bearing. Paper was used as a substrate.